1. Technical Field
The invention relates to direct access type magnetic storage systems including rigid disk drive systems and contact type read/record systems (e.g. floppy or diskette systems). More particularly the invention relates to apparatus for increasing fly height between a read head or slider and the recording media when positioned over a modified zone on the surface of the recording media.
2. Description of the Related Art
A disk drive (hard drive) is an information storage device which utilizes at least one rotatable magnetic disk to store information. The information is represented on the disk as a series of magnetically orientated regions. The magnetic regions are arrayed along the surface of the disk on either a plurality of concentric data tracks or spiral data tracks. Transducers generate magnetically orientated regions and sense such regions to store and read data on the disk.
In so-called hard drives, a transducer is mounted on a carrier called a slider. In operation, the slider flies just off the surface of the disk. Separation of the slider and disk reduces wear and consequent premature destruction of the components. An extremely low fly height of the slider is used to achieve high density data storage. High stability in fly height is required for accurate data storage, data signal reproduction and the avoidance of collision between slider and disk.
A slider flies as a result of the relative movement of the disk surface and the slider. This movement creates a cushion of air between the disk and the slider forcing the slider and the disk apart. The face of the slider toward the disk is known as the air bearing surface. Design of a slider air bearing surface, a suspension system for the slider and an actuator arm for slider positioning are directed to achieving a low mass assembly and a high degree of positional stability of the slider for a broad range of disk drive unit operating conditions.
The suspension system provides dimensional stability between the slider and the actuator arm by compensating for the force of the air between the air bearing surface and the disk surface as well as providing rapid motion damping of the slider following repositioning from one rack to another. The suspension system should control slider position relative to its directions of motion between tracks while resisting out-of-plane movement relative the preferred fly height above the disk surface. At no time during data read or write operations of the drive should the slider come into contact with the disk surface. The suspension typically comprises a load beam attached to the actuator arm and a flexure which connects the slider to the load beam. The load beam balances the slider by counteracting the lifting force from the spinning disk. The flexure supports the slider and allows flexibility during the slider's ride on the cushion of air.
A slider for a rigid disk drive is passive if its design automatically produces a constant fly height without active detection and correction. Common features of air bearing surfaces designed for passive devices are two air bearing rails running the length of the outside edges (i.e. the edges parallel to the direction of motion) of the slider. The slider may also include a tapered front edge. A Winchester slider adds a third rail centered between the outside edge rails. In positive pressure devices, the rails are separated by non air bearing surfaces. A read and write transducer is fabricated on the rear edge of the slider.
Reducing slider fly height is limited by head-disk interactions which increase as the slider gets closer to the disk. As the number of head disk interactions increase, the reliability of the system decreases. Head disk interactions may be caused by, for example, debris on the disk, on the slider, or by disk asperities.
A slider which reduces the number of head-disk interactions has greater reliability. Reducing the number of head-disk interactions has been accomplished by providing active devices in which a slider flies low during a read or write operation and returns to a higher, safer height between read/write operations. A disk drive generally includes a number of read/write heads, each mounted on a separate slider. A specific head is normally used for reading or writing less than 1 percent of the time. Thus, programmable designs have provided a substantial increase in reliability when compared to designs wherein the read/write head flies low all the time. However, they have the disadvantage of greater complexity.
Magnetic hard disk systems are usually permanently sealed and do not accept transferable disks. Transferable disks, such as used in floppy drives, are used in what are termed contact recording systems. A floppy drive uses diskettes, which in turn comprise a flexible disk housed in a plastic jacket. The plastic jacket has an inner liner of a nonwoven fabric facing the flexible disk. The liner wipes the surface of the disk clean as it rotates. Both sides of the flexible disk are covered with a particulate magnetic media (e.g. magnetic iron oxide suspended in a resin). In single sided drives, a spherical recording head is opposite a felt pad that urges the disk against the recording head. In two sided recording, a pair of head have opposing flat surfaces with reliefs running along their entire length, similar to a two rail slider for a hard disk system. While the heads are urged toward the recording media, the characterization of them as contact systems is only partially true. In many floppy disk drive designs contact between head and recording surface is intermittent. Contact between media and head is still undesirable because it results in wear of the read/write head over the long term. Recording head wear is a source of long term unreliability in contact recording systems having high speed, continuously spinning media.
Intermediate systems which utilize rigid media and contact recording are also known. The foregoing comments are also applicable to these systems.